1. Field of the Invention
The present invention relates to machines for erecting flat, collapsed tubular cartons and for filling and sealing the erected cartons. In particular, the present invention relates to a machine which increases production rate without significantly increasing cycle rate.
2. Description of the Prior Art
One common type of container in which liquid food products, such as milk and fruit juices are sold is a gable top carton made of paperboard or the like which has heat sealable top and bottom closure panels. In general, this type of carton is made of a high grade paperboard stock which is coated on both sides with a thermoplastic material such as polyethylene. The polyethylene coating on the paperboard is used for moisture-proofing, and is also a heat and pressure sensitive adhesive used to seal the top and bottom closure panels of the carton to make it liquid tight.
Automatic machines have been developed which erect flat, collapsed cartons of this type, form and seal the bottom ends of the carton, fill the cartons with the liquid product, and form and seal the top ends of the cartons. These machines generally include a rotatable mandrel assembly which is driven in a step-by-step indexing motion. The flat, collapsed cartons are withdrawn from a magazine, erected into an open-end tubular form and loaded onto each mandrel. As the mandrel assembly is rotated, the carton blank on the mandrel is sequentially advanced to work stations at which the bottom closure panels of the blank are broken, the bottom is heated, and the bottom is closed and sealed. Finally, each carton blank, with its bottom end sealed and its top end open, is withdrawn from its mandrel and deposited on a conveyor line. The cartons on the conveyor line are advanced through a top breaker unit at which the top panels are broken, a filling area at which the cartons are filled with the desired quantity of liquid, a defoamer area at which foam generated during the filling of the liquid is removed, a top heater area at which the polyethylene coating on the carton is heated, a top folding area at which the top panels are folded, and a top sealing area at which the tops of the cartons are sealed.
Examples of machines of this general type are shown in U.S. Pat. Nos. 3,088,380; 3,153,374; 3,405,505; and 3,669,160; and in British Pat. Nos. 709,454; 1,001,595; and 1,001,596.
There has been a continuing effort to increase the production rate of this type of machine. One way of increasing production rate, of course, is to run the machine at higher cycle rates. This approach, however, has practical limitations. The rate at which carton forming and sealing and the filling of liquid can be performed places practical limitations on the maximum cycle rate of the machine. In addition, as higher cycle rates are required, more complex mechanisms are often required. Higher cycle rates can also result in higher incidence of breakdown and the need for greater amounts of maintenance.
In the past, several approaches have been proposed to increase the production rate of machines of this type without significantly increasing cycle rate. For example, one type of machine uses four mandrel assemblies driven on a common horizontal axis. The four mandrel assemblies feed cartons onto four parallel, horizontal conveyor tracks. The cartons are advanced along the four tracks one step per cycle to the various work stations at which the cartons are filled and the top ends are formed and sealed. The four mandrel assemblies are arranged in four vertical planes which are parallel to the four conveyor tracks. This machine, therefore, is effectively four machines operating in parallel but driven by a common drive system. While this approach achieves a four-fold increase in production rate over a machine with a single mandrel assembly and a single conveyor line, there are significant disadvantages. In particular, because the four lines and four mandrel assemblies are in parallel with one another, access to the mechanisms of the two inner lines and inner mandrel assemblies is difficult. Since access is required in order to perform regular periodic maintenance and cleaning as well as for repairs, the use of four parallel conveyor lines and four parallel mandrel assemblies is extremely inconvenient. In addition, the use of four parallel conveyor lines and four parallel mandrel assemblies significantly increases the floor space required for the system, and results in approximately a four-fold increase in the number of parts and components of the machine.
Another approach to increasing production rate uses a mandrel assembly which rotates about a vertical axis. The mandrels all extend downward from the horizontal mandrel carriage or spindle. This system uses a pair of mandrels at each of a plurality of equally spaced positions around the horizontal mandrel carriage. Two cartons are erected and sealed simultaneously on the mandrel assembly. The two cartons are then deposited into a single conveyor line which carries each pair of cartons step-by-step along a horizontal track. Because two cartons are formed, filled and sealed simultaneously, twice the production is achieved with the same cycle rate. This type of system, however, also has disadvantages. The orientation of the mandrel carriage in a horizontal plane with a vertical axis of rotation takes up considerable floor space. In addition, in order to obtain a four-fold increase in production rate with the same cycle rate, two similar machines must be placed side-by-side. This proposed arrangement has not proved acceptable due to the large amount of floor space required and the problems presented in accessibility to certain components of the machines.
Still another proposal for increasing production rate also uses a horizontally aligned mandrel assembly which rotates about a vertical axis and which has pairs of mandrels extending downward from the mandrel carriage. The cartons are removed at the last work station around the mandrel assembly and are deposited into two separate conveyor tracks. The individual cartons are then indexed one at a time through the remainder of the machine. This arrangement achieves a two-fold increase in production rate, but again does not lend itself to further increases in production rate without doubling the floor space required by arranging two machines side-by-side.
Still another approach uses four mandrel assemblies arranged in two pairs. Each pair of mandrel assemblies is driven on a common horizontal axis, and each mandrel assembly is aligned in a vertical plane. One pair of mandrel assemblies feeds one horizontal conveyor track, and the other pair of mandrel assemblies feed another horizontal track. The vertical planes of the mandrel assemblies are perpendicular to the horizontal tracks. Cartons deposited in the horizontal tracks are moved in pairs stepwise through the remainder of the machine. As a result, a four-fold increase in production rate is achieved. This type of system, however, has the disadvantage that it consumes considerable floor space, due to the orientation of the mandrel assemblies. In addition, access to some parts of the machines can be difficult.
Still another approach to increasing cycle rates uses four mandrel assemblies which are driven on a common horizontal axis. Two of the mandrel assemblies feed cartons onto one horizontal conveyor track, while the other two mandrel assemblies feed cartons onto a second horizontal conveyor track. The vertical planes in which each of the mandrel assemblies are located are generally parallel to the horizontal conveyor tracks. This system uses a mechanical cross-over arrangement in order to feed two cartons at a time into each of the two conveyor tracks. The conveyor tracks then advance the cartons in pairs through the various work stations of the remainder of the machine. While this machine achieves a four-fold increase in production rate, it has increased complexity due to the feeding of cartons from two separate mandrel assemblies into a single conveyor line. In addition, having four mandrel assemblies on a common shaft for rotation presents problems with respect to accessibility of components positioned around the inner two mandrel assemblies, and requires greater power to rotate the four mandrel assemblies.
There is a continuing need for improved machines which erect flat, collapsed cartons and which fill and seal those cartons. In particular, there is a continuing need for machines which provide higher effective production rates without consuming excessive amounts of floor space and which permit easy accessibility to all components of the machine for service and maintenance adjustments.